The present invention relates to a digital signal recording method and a disk reproducing apparatus, and more particularly to such a method and an apparatus for recording a digital signal in the form of a data block on a disk adapted to be accessed by a host computer and for reproducing the digital signal from the disk.
A CD-ROM (CD-Read Only Memory) is a conventional example of this type of disk on which digital signals are recorded in units of a data block. Like the techniques described in Nikkei Byte, September 1994, p. 146, in the CD-ROM, data blocks composed of effective data and block addresses are recorded outward in order from the innermost track on the recording surface of the disk. When such a disk on which such data is recorded using the above technique is accessed and reproduced in accordance with a command from the host computer, a starting block address and a transfer block count are designated along with the access command, and desired data blocks are accessed and reproduced in accordance with such command and data.
Recently, disks each composed of two subdisks stuck to each other whose recording surfaces are readable from one side, disks having an upper recording surface and a lower recording surface whose recording surfaces are readable from one side, and disks each composed of two stuck-together sets of upper and lower recording surfaces which are readable from one side have been standardized. See, for example, the article xe2x80x9cConfidence in Unique Standards of DVDsxe2x80x9d, Nikkei Sanqyo Shinbun, Feb. 24, 1995, and the article xe2x80x9cSecond Stage of Struggle for DVD Standardsxe2x80x9d, Nihon Keizai Shinbun, Apr. 20, 1995.
When a digital signal is recorded using the above-mentioned technique on any of those disks having a plurality of recording surfaces, the host computer only recognizes the disks as having independent recording surfaces. In order to enable all of the recording surfaces to be accessed, the interface via which data is sent to and received from the host computer is required to be changed, and hence the conventional interface cannot be used as it is.
The above-mentioned technique has the problem that each time a recording surface to be reproduced is changed, it is necessary to read the innermost lead-in area before access and reproduction, such that it takes a long time to resume access and reproduction.
It is therefore an object of the present invention to provide a digital signal recording method and a disk reproducing apparatus which are capable of accessing at high speed all of the recording surfaces present in the disk and reproducing a digital signal using the conventional interface as it is.
In order to solve the above problem, in the digital signal recording method according to the present invention, a data frame is constructed which includes n (which is a natural number) data blocks recordable on a first digital signal recording surface and a second digital signal recording surface present on a disk and readable from one side of the disk, each data block being composed of a synchronization (sync) signal indicative of the boundary between the two data blocks, a block address indicative of the address of the data block on the recording medium, and data.
Further provided at the head of the data frame is a lead-in block having the same format as the data blocks and including information indicating the range of block addresses recorded on each of the recording surfaces of the disk, information indicating the configuration of the data frame, and a flag identifying a method for reproducing the data frame. The lead-in block and the data blocks of block addresses 1 to m (which is a natural number smaller than n) of the data frame are recorded on the first recording surface of the disk and the data blocks of block addresses (m+1) to n are recorded on the second recording surface of the disk. The disk has a multilayered structure with the corresponding recording surfaces. The first to m-th data blocks are arranged outward from the innermost track on the first recording surface and the (m+1)th to n-th data blocks are arranged inward from the outermost track on the second recording surface so as to enable the data blocks to be traced continuously.
The reproducing apparatus comprises means for processing a digital signal recorded on the disk in a predetermined format, means for sending/receiving commands and data to/from a host computer, means for controlling the whole apparatus in accordance with a command obtained by the sending/receiving means, means for moving a signal pickup to a desired position on the disk, means for controlling the focus of the signal pickup to access the recording surfaces selectively, means for controlling the rotational speed of a disk motor, means for detecting and recognizing the information included in the lead-in block indicating the range of block addresses recorded on a respective one of the recording surfaces of the disk, the information included in the lead-in block indicating the configuration of the data frame, and the flag included in the lead-in block identifying the method for reproducing the data frame, means for detecting the block address of a reproduced data block, means for calculating a block address at which the reproduction ends in accordance with a command from the host computer, and means for generating a command which controls the access to the disk and reproduction of a signal from the disk in accordance with the information obtained by the detection and recognition of the flag, the detected block address, and the result of the calculation.
According to such a structure, since consecutive block addresses are allocated to the respective data blocks recorded on all of the recording surfaces of the disk, all of the recording surfaces of the disk can be accessed and reproduced at high speed by using the conventional interface.
Other objects, features, and advantages of the invention will become apparent from the following detailed description of an embodiment of the invention taken in conjunction with the accompanying drawings.